Vehicles often include a suspension system to aid in regulating the vehicle's ride and handling. Many suspension systems include control arms, which connect a wheel assembly to the frame and/or body of a vehicle. The geometry of a control arm varies from vehicle to vehicle. The geometry of the control arm may also vary depending on the desired ride and handling characteristics and overall suspension design. The geometry of a control arm may determine the angle of the wheel in relation to a road surface, for example camber, caster, or toe.
Camber angle is a measure of how much a wheel and tire assembly on a vehicle leans or tilts, either inward toward, or outward from, the vehicle, when viewed from the front or back. As such, the camber angle can be defined in different ways by measuring the relative positions of various components on a vehicle. Where the wheel/tire assembly is tilted such that the upper part of the wheel/tire assembly is closer to the centerline of the vehicle than the bottom of the tire, the camber is said to be negative. Where the top of the wheel/tire assembly is farther from the centerline of the vehicle than the bottom of the tire, the camber angle is said to be positive.
The caster angle is typically defined by the angle between a vertical line and a line drawn through upper and lower steering pivots, as viewed from either side of the vehicle. As such, the caster angle can be defined in different ways by measuring the relative positions of various components on a vehicle. For example, the caster angle can be defined as the angle between a vertical line and a caster reference line drawn either through an upper strut mount and a lower ball joint or through an upper ball joint and the lower ball joint.
The toe angle is typically defined by the angle between a horizontal line drawn down the centerline of the vehicle and a line drawn perpendicular to the center axis of the tire and wheel assembly as viewed from either above or below. As such, the toe angle can be defined in different ways by measuring the relative positions of various components on a vehicle. Where the forward edge of the wheel/tire assembly is closer to the mid-plane of the vehicle than the back edge, the toe angle is said to be positive. Where the forward edge is farther from the mid-plane, the toe angle is said to be negative.
Automotive manufacturers publish specifications for camber, caster, and toe for each model of vehicle. Many vehicles are designed with a means of adjustment of these alignment angles for use in vehicle maintenance, but some vehicles are designed without a built in adjustment or insufficient adjustment to achieve desired settings. Adjustment of the camber, caster, and toe angles will affect tire wear and handling characteristics of a vehicle. For example, camber may be altered to allow for differing cornering characteristics. In some cases, these angles, and therefore a vehicle's handling characteristics, may be adjusted by choosing control arms having different geometry. In addition, when replacing damaged, worn out, or factory-installed control arms with new control arms, the new control arm may have a slightly different geometry. Changing of control arms on a vehicle often requires difficult and time-consuming adjustments. Thus, a vehicle owner may choose to forego correcting undesirable ride and handling characteristics to avoid the expense and difficulty of servicing control arms. Alternately, there are adjustable control arms on the market that can change the wheel alignment angles to a desired setting, however these arms may violate factory fit and form or they may give up arm strength in order to achieve change.
What is needed is an adjustment mechanism that allows a vehicle owner or technician to alter control arm geometry to fit different vehicles and/or to easily alter the alignment parameters—and thus handling and/or tire wear of a vehicle without the need to remove or exchange a control arm. Additionally a control arm that is easily adjustable should be provided in a package similar to the original-equipment control arm to avoid contact with other parts of the vehicle. The design of a control arm should be such that inherent strength is maximized by eliminating or minimizing unnecessary loading upon the internal structure of the arm, thus optimizing mass, volume, and/or material strength requirements.
The adjustable control arm presented here provides for adjustment of control arm geometry—and thus vehicle alignment angles—via a multi-piece structure, which may avoid the need to remove the wheel assembly and/or the control arm from the vehicle while maintaining a minimal package space in the wheel well. Furthermore, the adjustable control arm presented here maximizes strength of the control arm assembly by directing the vehicle's dynamic motion forces along the axes of the adjustment mechanism.